1. Technical Field
This invention relates to active noise control, and more specifically to adjustment of the size and/or shape of one or more quiet zones within a listening space where the active noise control is functioning to reduce undesired sound.
2. Related Art
Active noise control may be used to generate sound waves or “anti noise” that destructively interferes with undesired sound waves. The destructively interfering sound waves may be produced through a loudspeaker to combine with the undesired sound waves in an attempt to cancel the undesired noise. Combination of the destructively interfering sound waves and the undesired sound waves can eliminate or minimize perception of the undesired sound waves by one or more listeners within a listening space.
An active noise control system generally includes one or more microphones to detect sound within an area that is targeted for destructive interference. The detected sound is used as a feedback error signal. The error signal is used to adjust an adaptive filter included in the active noise control system. The filter generates an anti-noise signal used to create destructively interfering sound waves. The filter is adjusted to adjust the destructively interfering sound waves in an effort to optimize cancellation within the area. Larger areas may result in more difficultly optimizing cancellation. Moreover, in many cases, listeners are only in certain areas within a larger listening area. Therefore, a need exists to optimize cancellation within one or more regions within the larger listening area. In addition, a need exists to adjust optimized cancellation to occur in the different regions.